Brachythecium acutum

(Mitten) Sullivant

Icon. Musc., suppl., 99. 1874.

Endemic
Basionym: Hypnum acutum Mitten J. Linn. Soc., Bot. 8: 33, plate 6 [upper right]. 1864
Synonyms: Brachythecium pseudocollinum Kindberg
Treatment appears in FNA Volume 28. Treatment on page 423. Mentioned on page 415, 416, 419, 426, 427.

Plants medium-sized to large, in loose to dense mats, yellowish to brownish. Stems to 7 cm, creeping, terete or occasionally subcomplanate-foliate, irregularly pinnate, branches to 8 mm, straight, terete to subcomplanate-foliate. Stem-leaves erect to erect-spreading, loosely imbricate to somewhat spaced, broadly to narrowly ovate-triangular, broadest at 1/10 leaf length or below, not concave, not or slightly plicate, 2–2.8 × 0.8–1.2 mm; base rounded, inconspicuously short-decurrent; margins plane, occasionally recurved distally, minutely and evenly serrulate to subentire; apex gradually tapered to narrow acumen or gradually acuminate, occasionally short-apiculate; costa to 60–70% leaf length, strong, terminal spine absent; alar cells subquadrate or short-rectangular, small to enlarged, 15–30 × 10–14 µm, walls moderately thick, region somewhat differentiated or almost undifferentiated, usually inconspicuous, of 4–7 × 5 cells, pellucid; laminal cells linear, 60–135 × 8–11 µm, walls not or moderately porose; basal-cells to 20–25 × 10–13 µm, region in 2–5 rows. Branch leaves with margins often recurved at base, usually less serrulate; basal laminal cells almost undifferentiated or alar region of 2–7 cells, pellucid, (often hidden by recurved margins). Sexual condition autoicous. Seta redbrown, 2–4 cm, smooth. Capsule inclined to horizontal, redbrown, ovate, slightly curved, 15–20 mm; annulus separating by fragments; operculum conic. Spores 13–18 µm.


Habitat: Wet soil, peat, fens, swamps, rotten logs in swampy forests
Elevation: low to moderate elevations (0-1000 m)

Distribution

V28 654-distribution-map.gif

B.C., Man., Nfld. and Labr. (Nfld.), Nunavut, Ont., Que., Sask., Yukon, Alaska, Calif., Colo., Del., Idaho, Ill., Ind., Iowa, Maine, Mo., Mont., Nebr., N.J., N.Y., N.Dak., Ohio, Pa., S.Dak., Utah, Wyo.

Discussion

Brachythecium acutum is distinguished by the evenly tapered, triangular, and weakly or not plicate leaves. Brachythecium acutum has been treated as an eplicate form of B. salebrosum (for example, H. A. Crum and L. E. Anderson 1981). This conclusion may have been based on the fact that sometimes, especially in drier habitats, its alar cells are relatively smaller and form a square group; this pattern is also known for the Eurasian B. mildeanum (Schimper) Schimper. However, optimally developed B. acutum is distinct in having homogeneous areolation across the leaf base, quite regularly triangular leaves, minute teeth along leaf margins, not or very weakly plicate leaves, and unusually long setae.

Selected References

None.

Lower Taxa

None.

"long" is not a number."broad" is not a number.

... more about "Brachythecium acutum"
acuminate +
dioicous +, autoicous +  and sexual +
Michael S. Ignatov +
(Mitten) Sullivant +
10um +  and 13um +
autoicous +  and sexual +
autoicous +  and sexual +
short-decurrent +
rounded +  and narrowed +
rounded +
short to long +
Hypnum acutum +
subcomplanate-foliate +
cucullate +
inclined +  and horizontal +
1.5 cm15 mm <br />0.015 m <br /> (2 cm20 mm <br />0.02 m <br />) +
specialized +
synoicous +, dioicous +, autoicous +, sexual +  and asexual +
short-rectangular +  and subquadrate +
small +  and enlarged +
differentiated +
10um +  and 14um +
3 (?) +  and 2 (?) +
discernible +
B.C. +, Man. +, Nfld. and Labr. (Nfld.) +, Nunavut +, Ont. +, Que. +, Sask. +, Yukon +, Alaska +, Calif. +, Colo. +, Del. +, Idaho +, Ill. +, Ind. +, Iowa +, Maine +, Mo. +, Mont. +, Nebr. +, N.J. +, N.Y. +, N.Dak. +, Ohio +, Pa. +, S.Dak. +, Utah +  and Wyo. +
low to moderate elevations (0-1000 m) +
not adherent +
Wet soil, peat, fens, swamps, rotten logs in swampy forests +
8um (?) +  and 11um (?) +
concave +
pointed +
moderate to somewhat +
entire +, serrulate +  and serrate +
evenly serrulate +  and subentire +
perfect +  and xerocastique +
hygrocastique +
not plicate +  and crumpled +
Icon. Musc., suppl., +
inconspicuous +  and undifferentiated +
differentiated +
2 (?) +  and 5 (?) +
2 cm20 mm <br />0.02 m <br /> (4 cm40 mm <br />0.04 m <br />) +
spaced;imbricate to somewhat;imbricate;imbricate to somewhat +
erect +  and erect-spreading +
ovate-triangular +
0.8mm;1.2mm +
subcomplanate-foliate +
not reddish +
arching +, erect +, ascending +  and creeping +
0 cm0 mm <br />0 m <br /> (7 cm70 mm <br />0.07 m <br />) +
Brachythecium pseudocollinum +
Brachythecium acutum +
Brachythecium +
species +
incrassate +
yellowish +  and brownish +
medium-sized;large +